Alkaline papers, aging

No specific information on the possible effect of the synthetic sizes on permanence is available, and they are not mentioned in the standard 04), but it seems unlikely that they would be deleterious. Presumably they have been used in comnercial grades of neutral/alkaline paper subjected to accelerated ageing tests. In terms of general effects on paper, the synthetic sizes have a tendency to reduce the surface frictional properties of paper to a greater extent than rosin. For example, this makes it more difficult to stack piles of cut sheets without slippage. However, the effect is less noticeable when high proportions of chalk filler are used, because the blocky particles increase friction. 

While Barrow solved the main problem, there are other modes of degradation which must be considered. As an organic material, cellulose and paper can be easily oxidized. Very small amounts of the transition metals, compounds of iron, copper, and cobalt, under humid conditions can accelerate oxidation and embrittlement of paper. This type of degradation, as is shown later, does not show up in the dry-oven accelerated aging which Barrow used. Thus his alkaline papers, if they contained the oxidation catalysts, may not always have been permanent. 

Three alkaline papers performed well after 36 years of natural aging, but retention of properties was not as great as expected (24). 

Another group of effective sizes include alkyl ke-tene dimers (- fatty diketenes) and alkenylsucci-nic anhydrides. These products react with the OH-groups of the cellulose fiber. While rosin-based sizes can only by used in acid paper making processes, the cellulose-reactive sizes are used in neutral and alkaline paper making. The result is better sheet strength, reduced corrosion on the equipment, less salt in the effluent and better stability of the paper towards aging (archival paper). 

Locock, A.J. 1994. Aspects of the geochemistry and mineralogy of the Ice River alkaline intrusive complex, Yoho National Park, British Columbia. MSc thesis. University of Alberta, Edmonton, Alberta. Parrish, R.R., Heinrich, S., Archibald, D. 1987. In Radiogenic Age and Isotopic Studies Report 1, Geological Survey of Canada, Paper 87-2, 33-37. 

All too often, the environment within library and archive storage areas presents a threat to their aging collections, when it could be utilized as a most cost-effective tool for their preservation. All paper-based materials, whether rare or common-place, old or new, acid or alkaline, are susceptible to heat and humidity. While it is... 

Old manuscripts printed on high grade paper with acid inks, in particular the iron inks commonly used in the Middle Ages, showed significantly greater deterioration than manuscripts printed with neutral or alkaline inks (2). 

Fillers. The buffering action of an alkaline filler is necessary to ensure permanence in filled paper. Retained alkalinity in the paper as it ages would resist any drop in pH that might result from absorption of either carbon dioxide or sulfur dioxide from the air. Acidic fillers, such as certain types of clay, accelerate the aging process. Calcium carbonate is an ideal filling material for permanent paper as well as for some grades not requiring permanency. In fact, the work of Barrow made the use of calcium carbonate a requirement in the manufacture of permanent book papers (1). 

There is a striking difference, however, in the action of various alkaline materials. Neutralizing acid paper with sodium carbonate, as is shown later, prolongs its life. Alkalizing paper to pH 10 with sodium carbonate causes paper to darken, to oxidize, and to degrade. The effects are most pronounced in humid-oven accelerated aging, less so in the dry-oven aging. 

Figures 4 and 4A and Table IV show the results when the paper was neutralized by immersion in 0.1% sodium carbonate. The aging results are now surprisingly good, almost equal to those obtained with magnesium as given in Figure 2 and Table I. The paper, however, does not have an alkaline reserve and will not be stable in an acid atmosphere. Furthermore, as the next experiment shows, an alkaline reserve cannot be established using sodium carbonate.

Trier (34) described one bulked paper as being loaded with microspheres of a copolymer of vinylidene chloride and acrylonitrile. Such polymers are known to split off hydrochloric acid. While this may have occurred in oven aging, the pH of the sample did not drop below 7 so acid degradation does not seem to have been involved. On the other hand, the paper did degrade rapidly in the humid oven, and this was very well corrected by the KI treatment. From the evidence in the literature peroxides and, through the catalysts, free radicals appear to be at work, which the KI corrected. This is an application that recalls its use in oxygen-alkaline pulping and in the prevention of the peroxide defects in microfilm. 

Using the normal titration method on morpholine-treated paper samples, reserve alkalinity levels of less than 1% are found. However, in view of the previously mentioned possibilities for interaction between cellulose and morpholine and the observed reduction in the aging rate of morpholine-treated paper, it was thought likely that morpholine could be present in a form not immediately titratable but which might still offer some degree of protection against acid attack. 

The effect of acidity caused by alum-rosin size has been obviated by the substitution of sizing agents which are effective slightly on the alkaline side of neutrality. It has been established that papers of satisfactory permanence can be manufactured with such sizes. It is possible to use rosin as a size and to avoid the conjunction with alum by a number of processes. There are insufficient data on the aging characteristics of paper sized with the available modified rosin sizes to judge the effect on permanence. Possible reactions of the rosin, such as oxidation and formation of peroxides, must be considered. 

Papers which are acidic as manufactured can be stabilized by a deacidification procedure. Several processes have been developed for this purpose, the most successful of which provide neutralization of the acid present and leave a residue such as calcium carbonate or magnesium carbonate as reserve alkalinity in the paper. This alkalinity serves to protect the paper as acidity develops from paper components during aging or is introduced by atmospheric contamination. The amount of reserve alkalinity can be determined by adding a measured volume of standard acid solution in excess to a weighed specimen of the paper and back-titrating the excess to neutrality with standard base solution. 

A much more recent development is the morpholine process in which fifty books per hour are treated in an evacuated chamber with morpholine-water vapor (12). In its present form, it was effective on 95% of the papers treated, prolonging their life on average by a factor of 4-5 (Figure 7). Though it does not leave a titratable alkaline reserve in the paper, acid papers treated in this manner aged in the presence of 5 ppm S02 at 75 °C and 60% relative humidity deteriorate more slowly than if untreated. Recent tests of twenty treated books at the Library of Congress show that their pH has not declined in two years. The equipment for the process was set up in the Virginia State Library where 35,000 books were treated in the first seven months of operation. 

Curators, collectors, and conservators need to be on constant guard against acidic tissue paper that has discolored with age. Textiles stored with highly acid tissue papers also will become discolored with time. There are acid-free and alkaline-buffered tissue papers commercially available through archival paper and supply firms. In the last several years, paper companies have become aware of the needs of historic textiles and costume departments in museums, historical societies, and universities and are placing into production acid-free rolling tubes, tissue paper, and storage boxes for costumes and accessories. 

Recent approaches directed toward preventing oxidation of cotton cloth included using accelerated aging of alkaline-treated cotton cloth for neutralization of acidic, oxidized, cellulose decomposition components that in cellulosic textiles and in paper are responsible for age tendering and yellowing. Conclusions regarding the relative effectiveness of treatments at room temperature were based on results of treatments at one elevated temperature (8). Predictions of long-term effects of these treatments are unknown (9). 

Application of Additives to Silk. Deacidifying Agent. This material is ethoxymagnesium ethyl carbonate dissolved in trichlorotrifluoroethane (Wei To Associates). It has been extensively used as an alkaline buffering agent to protect paper and cellulosic textiles from aging (7,8,21). Samples were dipped one at a time in the solution for 30 s and then dried flat on a sheet of poly(methyl methacrylate). The treated samples had an add-on of approximately 3% and were relatively stiff. 

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